Amiodarone

Amiodarone

[100mg tablet 64 cents, 200mg tablets $1.02; 1 vial for IV injection $6.08]

ADMINISTRATION ROUTES:

  • IV, PO, NG

ALTERNATIVE NAMES:

  • Cordarone-X

ICU INDICATIONS:

  1. VT,VF
  2. Atrialtachycardias

PRESENTATION AND ADMINISTRATION:

  • PO / NG:
    200mg tablets; tablets may be crushed for NG administration
  • IV:
    150mg in 3ml ampoules. Cordarone IV is a sterile clear, pale-yellow solution visually free from particulates. Compatible with D5W only
    Do not use PVC infusion bags for infusion as adsorption may occur. When mixing for infusion use only EXCEL container 250ml bags of 5% dextrose Injection USP. Add 450mg amiodarone.
    For stat dose (usually 300mg) add to a standard 100ml plastic bag of D5W. Administration via a central line is preferred
    Store at room temperature; do not refrigerate.

DOSAGE:

  • Tachydysrhythmias:
    IV load 300-450mg in 100ml D5W over 20 minutes to two hours
    Ongoing infusion: 450 mg in 250ml glucose 5% over 12 hours x 2 i.e. 900mg over 24 hours
    Dilute in glucose 5% only using Excel Container 250ml 5% Dextrose Injection USP.

    Note: 300mg stat may be considered for VT/VF (this should be added to 10-20ml of D5W and administered by slow IV push over 3 minutes or more)

    Transition from IV to oral therapy:
    200mg PO 8 hourly for 1 week followed by 200mg PO 12 hourly for one week followed by 200mg PO 12-24 hourly thereafter

    Note: higher oral dosages (up to 1600mg per day can be used in patients who have not received a full IV load). An overlap of intravenous and oral medication of up to two days is recommended.

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

  • Dose as in normal renal function

DOSAGE IN PAEDIATRICS:

  • The safety and efficacy of amiodarone in the pediatric population have not been established; therefore, its use in paediatric patients is not recommended.

CLINICAL PHARMACOLOGY:

  • Amiodarone is generally considered a Class III antiarrhythmic drug, but it possesses electrophysiologic characteristics of all four Vaughan Williams classes.

CONTRAINDICATIONS:

  1. known hypersensitivity to any of the components of amiodarone, including iodine.
  2. second-or third-degree AV block unless a functioning pacemaker is available.

WARNINGS

  • Hypotension:
    Hypotension is the most common adverse effect seen with amiodarone. Hypotension should be treated by vasopressor drugs, positive inotropic agents, and volume expansion. Slowing the rate of infusion may also be effective.
  • Bradycardia and AV Block:
    Drug-related bradycardia should be treated by discontinuing amiodarone. Additional measures including drug therapy and/or temporary pacing may be required if bradycardia does not resolve.

PRECAUTIONS

  • General:
    Liver enzyme elevations in patients on amiodarone are not uncommon; however, baseline abnormalities in hepatic enzymes are not a contraindication to treatment. Rare cases of fatal hepatocellular necrosis after treatment with amiodarone have been reported.
    Like all antiarrhythmic agents, amiodarone may cause a worsening of existing arrhythmias or precipitate a new arrhythmia.
    There have been reports of acute-onset (days to weeks) pulmonary injury in patients treated with amiodarone. Findings have included pulmonary infiltrates on X-ray, bronchospasm, wheezing, fever, dyspnea, cough, hemoptysis, and hypoxia. Some cases have progressed to respiratory failure and/or death.
  • Laboratory Tests:
    Consider measurement of thyroid function as a baseline (if not measured previously).
  • Drug/Laboratory Test Interactions:
    Amiodarone alters the results of thyroid-function tests, causing an increase in serum T4 and serum reverse T3, and a decline in serum T3 levels. Despite these biochemical changes, most patients remain clinically euthyroid.

IMPORTANT DRUG INTERACTIONS FOR THE ICU

  • Amiodarone with:
    Cyclosporine: increased cyclosporine levels; dosage reduction of cyclosporine required
    Digoxin: increased digoxin levels; dosage reduction of digoxin required.
    Antiarrhythmics: in general, any added antiarrhythmic drug should be initiated at a lower than usual dose with careful monitoring.
    Antihypertensives: beta blockers and calcium channel blockers may lead to increased risk of bradycardia when combined with amiodarone
    Warfarin: dose of warfarin should be reduced by 1/2 to 1/3rd and INR should be closely monitored
    Rifampin:decreases in serum concentrations of amiodarone.
    Fluoroquinolones: increased risk of QTc prolongation when combined with amiodarone
    Macrolides: increased risk of QTc prolongation when combined with amiodarone

ADVERSE REACTIONS

  • Body as a Whole:
    Fever
  • Cardiovascular System:
    Bradycardia, congestive heart failure, hypotension, ventricular tachycardia
  • Respiratory System:
    Dyspnea, cough, hemoptysis, wheezing, hypoxia, pulmonary infiltrates
  • Digestive System:
    Nausea, deranged LFTs
  • Nervous System:
    Hallucinations, confusional state, pseudotumor cerebri
  • Endocrine System:
    Hypothyroidism, hyperthyroidism, SIADH
  • Skin:
    Toxic epidermal necrolysis

Critical Care Drug Manual

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